IMO bard 9/xxx is the bare minimum. Although I prefer a bare minimum of bard 10. At bard 9 you get inspired greatness +2 attack +1 fort +temp hp. I choose 10 because I play warchanter and I still like to have music of the dead and music of the maker to fascinate undead and constructs. The only way to get these two songs (unless you are a virtuoso which I often do up to lvl 10 as stated in previous threads ) is by taking extra song IV (min lvl 10). Finally you get 2 lvl 4 spells that I think are crucial FOM, and DD.
As I have stated in previous threads with the lvl cap increasing I would have changed my Ska build around (10bard/4ftr/2rog GTWF,SB,QD,EXTEND,TOUGHNESS,PA,WF:slash)a bit. I will be curious to see if they implement Superior TWF at which a BAB of 15 will be needed and only obtainable by taking a lvl of fighter at 20 to get the extra feat at a BAB of 15.
For now I will collect ingredients for my next Bard build.